“connection file” — Specifies the name of an .rdp file for the connection.

/v:<server[:port]> — Specifies the remote computer to which you want to
connect.

/admin — Connects you to the session for administering a server.

/f — Starts Remote Desktop in full-screen mode.

/w:<width> — Specifies the width of the Remote Desktop window.

/h:<height> — Specifies the height of the Remote Desktop window.

/public — Runs Remote Desktop in public mode.

/span — Matches the remote desktop width and height with the local
virtual desktop, spanning across multiple monitors if necessary. To span
across monitors, the monitors must all have the same height and be aligned
vertically.

/edit — Opens the specified .rdp connection file for editing.

/migrate — Migrates legacy connection files that were created with
Client Connection Manager to new .rdp connection files.

[OK]

Update: But if you are extremly unlucky, you wont be able to connect to it at all.

[Window Title]

Remote Desktop Disconnected

[Content]

Your Remote Desktop session has ended, possibly for one of the following reasons:

The administrator has ended the session.

An error occurred while the connection was being established.

A network problem occurred.

For help solving the problem, see “Troubleshoot Remote Desktop problems” in Help and Support.

[OK] [Help]

[Window Title]

Remote Desktop Disconnected

[Content]

Your Remote Desktop session has ended, possibly for one of the following reasons:

The administrator has ended the session.

An error occurred while the connection was being established.

A network problem occurred.

For help solving the problem, see “Troubleshoot Remote Desktop problems” in Help and Support.

[OK] [Help]

I had to attach a keyboard and a screen to the server just to realize a reboot would probably fix the issue – which it did. So if in doubt reboot.